To debug most Wireguard issues you'll need to examine the node that has the leadership or the Wireguard server itself.

View Wireguard configuration (server)

The wg show all command will detail the peer connections, the peers being the kube-vip leader on the remote cluster.

# wg show all
interface: wg0
  public key: g1siqaKYbmAAIM4PxBrzybA2BaKmkzLxG7a2Ffb5sho=
  private key: (hidden)
  listening port: 51820

peer: Zl4q4n6aLOJcLvNxzbsknpUccvJxlXg/e3isNjBF5Gk=
  allowed ips:
  latest handshake: 1 minute, 21 seconds ago
  transfer: 4.25 MiB received, 1.05 MiB sent

An allowed ips: (none) configuration

In the event an peer has no allowed IPs it usually means that two peers were created with the same ip range (which is illegal in Wireguard)

Enable Wireguard debugging (on the server)

echo module wireguard +p > /sys/kernel/debug/dynamic_debug/control

Logs can be found with dmesg